text: /*
   * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
   * Copyright (c) 1996-1999 by Internet Software Consortium.
   *
   * Permission to use, copy, modify, and distribute this software for any
   * purpose with or without fee is hereby granted, provided that the above
   * copyright notice and this permission notice appear in all copies.
   *
   * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
   * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
   * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
   * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   *
   * $Id: inet_ntop.c,v 1.5 2005/11/03 22:59:52 marka Exp $
   */
  
  #include "port_before.h"
  
  #include <sys/param.h>
  #include <sys/types.h>
  #include <sys/socket.h>
  
  #include <netinet/in.h>
  #include "arpa/inet.h"
  #include <arpa/nameser.h>
  
  #include <errno.h>
  #include <stdio.h>
  #include <string.h>
  
  #include "port_after.h"
  
  /*%
   * WARNING: Don't even consider trying to compile this on a system where
   * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
   */
  
  static const char *inet_ntop4(const u_char *src, char *dst, size_t size);
  static const char *inet_ntop6(const u_char *src, char *dst, size_t size);
  
  /* const char *
   * inet_ntop(af, src, dst, size)
   *	convert a network format address to presentation format.
   * return:
   *	pointer to presentation format address (`dst'), or NULL (see errno).
   * author:
   *	Paul Vixie, 1996.
   */
  const char *
  inet_ntop(int af, const void * __restrict src, char * __restrict dst,
      socklen_t size)
  {
  	switch (af) {
  	case AF_INET:
  		return (inet_ntop4(src, dst, size));
  	case AF_INET6:
  		return (inet_ntop6(src, dst, size));
  	default:
  		errno = EAFNOSUPPORT;
  		return (NULL);
  	}
  	/* NOTREACHED */
  }
  
  /* const char *
   * inet_ntop4(src, dst, size)
   *	format an IPv4 address
   * return:
   *	`dst' (as a const)
   * notes:
   *	(1) uses no statics
   *	(2) takes a u_char* not an in_addr as input
   * author:
   *	Paul Vixie, 1996.
   */
  static const char *
  inet_ntop4(const u_char *src, char *dst, size_t size)
  {
  	static const char fmt[] = "%u.%u.%u.%u";
  	char tmp[sizeof "255.255.255.255"];
  	int l;
  
  	l = snprintf(tmp, sizeof(tmp), fmt, src[0], src[1], src[2], src[3]);
  	if (l <= 0 || (socklen_t)l >= size) {
  		errno = ENOSPC;
  		return (NULL);
  	}
  	strlcpy(dst, tmp, size);
  	return (dst);
  }
  
  /* const char *
   * inet_ntop6(src, dst, size)
   *	convert IPv6 binary address into presentation (printable) format
   * author:
   *	Paul Vixie, 1996.
   */
  static const char *
  inet_ntop6(const u_char *src, char *dst, size_t size)
  {
  	/*
  	 * Note that int32_t and int16_t need only be "at least" large enough
  	 * to contain a value of the specified size.  On some systems, like
  	 * Crays, there is no such thing as an integer variable with 16 bits.
  	 * Keep this in mind if you think this function should have been coded
  	 * to use pointer overlays.  All the world's not a VAX.
  	 */
  	char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
  	struct { int base, len; } best, cur;
  	u_int words[NS_IN6ADDRSZ / NS_INT16SZ];
  	int i;
  
  	/*
  	 * Preprocess:
  	 *	Copy the input (bytewise) array into a wordwise array.
  	 *	Find the longest run of 0x00's in src[] for :: shorthanding.
  	 */
  	memset(words, '\0', sizeof words);
  	for (i = 0; i < NS_IN6ADDRSZ; i++)
  		words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
  	best.base = -1;
  	best.len = 0;
  	cur.base = -1;
  	cur.len = 0;
  	for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
  		if (words[i] == 0) {
  			if (cur.base == -1)
  				cur.base = i, cur.len = 1;
  			else
  				cur.len++;
  		} else {
  			if (cur.base != -1) {
  				if (best.base == -1 || cur.len > best.len)
  					best = cur;
  				cur.base = -1;
  			}
  		}
  	}
  	if (cur.base != -1) {
  		if (best.base == -1 || cur.len > best.len)
  			best = cur;
  	}
  	if (best.base != -1 && best.len < 2)
  		best.base = -1;
  
  	/*
  	 * Format the result.
  	 */
  	tp = tmp;
  	for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
  		/* Are we inside the best run of 0x00's? */
  		if (best.base != -1 && i >= best.base &&
  		    i < (best.base + best.len)) {
  			if (i == best.base)
  				*tp++ = ':';
  			continue;
  		}
  		/* Are we following an initial run of 0x00s or any real hex? */
  		if (i != 0)
  			*tp++ = ':';
  		/* Is this address an encapsulated IPv4? */
  		if (i == 6 && best.base == 0 && (best.len == 6 ||
  		    (best.len == 7 && words[7] != 0x0001) ||
  		    (best.len == 5 && words[5] == 0xffff))) {
  			if (!inet_ntop4(src+12, tp, sizeof tmp - (tp - tmp))) {
  				errno = ENOSPC;
  				return (NULL);
  			}
  			tp += strlen(tp);
  			break;
  		}
  		tp += sprintf(tp, "%x", words[i]);
  	}
  	/* Was it a trailing run of 0x00's? */
  	if (best.base != -1 && (best.base + best.len) == 
  	    (NS_IN6ADDRSZ / NS_INT16SZ))
  		*tp++ = ':';
  	*tp++ = '\0';
  
  	/*
  	 * Check for overflow, copy, and we're done.
  	 */
  	if ((socklen_t)(tp - tmp) > size) {
  		errno = ENOSPC;
  		return (NULL);
  	}
  	strcpy(dst, tmp);
  	return (dst);
  }
  
  /*
   * Weak aliases for applications that use certain private entry points,
   * and fail to include <arpa/inet.h>.
   */
  #undef inet_ntop
  __weak_reference(__inet_ntop, inet_ntop);
  